In MPTP-induced mouse PD models, TREM2 inhibited neuroinflammatory responses and reduced MPTP-induced neuropathic changes by inhibiting toll-like receptor 4(TLR4)/tumor necrosis factor receptor-associated factor 6 (TRAF6)-mediated nuclear factor-κB (NF-κB) and MAPK signaling activation (51). This evidence concerns the gene TLR4 and Parkinson disease.